Engines, as well as other machines, may include a transmission device, in which power is transmitted through a flexible transmission medium such a chain, a belt or the like, as shown in FIG. 12. A sliding contact guide, which can be either a movable guide Ga or a fixed guide Gb, may be provided in sliding contact with the transmission medium, such as chain CH, for guiding the transmission medium and limiting its path of travel. The movable guide and the fixed guide prevent vibration of the power transmitting medium CH, both in, and transverse to, its plane of travel. The movable guide also cooperates with a tensioner T to impart appropriate tension to the transmission medium. These sliding contact guides are attached to a frame of the engine E or other machine by means of shafts P, which may be mounting bolts, mounting pins, or the like.
FIG. 9 shows, in elevational view, a plastic movable guide 300, also referred to as a tensioner lever, which is used in a chain transmission. This guide is described in Japanese Patent Application No. 2000-382798.
FIG. 10 is a bottom plan view of the plastic movable guide of FIG. 9.
In this plastic movable guide 300, a guide body 301 includes a shoe 302 having a surface which is in sliding contact with a power transmission medium such as a traveling chain CH or a belt. The guide also comprises a plate-receiving portion 303 extending along the longitudinal direction of the guide on the back of the shoe 302. The shoe and plate-receiving portion are integrally molded as a unit from a synthetic resin. A reinforcing plate 308, composed of a rigid material, reinforces the guide body 301, fits into a slot 307 in the plate-receiving portion 303. The slot extends along the longitudinal direction of the guide and its opening faces in a direction opposite to the direction in which the chain-engaging surface of the shoe faces. A mounting hole 305 is provided adjacent one end of the plate-receiving portion 303 for mounting the guide body on a mounting shaft. A hole 308A is also provided in the reinforcing plate 308. The hole 308A is brought into register with the mounting hole 305 in the guide body 301 when the reinforcing plate is fitted into the slot in the plate-receiving portion of the guide body, so that the guide body and reinforcing plate may be fastened together on the mounting shaft.
In the plastic movable guide 300, the guide body 301, which includes the shoe 302 and the plate-receiving portion 303 on the back of the shoe, is molded from a synthetic resin. The guide body 301 engages the transmission medium in sliding contact therewith, therefore it is not necessary to provide a separate shoe member. Consequently the number of parts, and the number of production steps needed to produce the guide, are reduced. Furthermore, since the slot 307 extends in the longitudinal direction of the guide, its opening is situated in an edge of the plate-receiving portion 303 in the guide body 301, and a reinforcing plate 308 is fitted into the slot, the strength of the guide in the pivoting direction is increased, and its bending rigidity and toughness are significantly improved.
The above-described plastic movable guide is mounted on a shaft such as a mounting bolt or the like, the shaft being received in the mounting hole in the guide body and the hole in the reinforcing plate. These holes must be correctly positioned in register with each other, and positioning of the holes in the process of assembling the guide required considerable time. Furthermore, when reinforcing plates used in the conventional guide are punched out of a rolled material M or the like, as shown in FIG. 11, the areas of the unused portions NG of the rolled material M are large. The resulting low yield contributes to a high production cost. These problems exist not only in the production of movable guides, but also in the production of fixed sliding contact guides in which a reinforcing plate is fitted into a slot in the guide body.
Another problem with conventional guides is the demand for reduced weight in the guides resulting from the high cost of fuel.
The inventors have aggressively examined and analyzed the load distribution in the above-described sliding contact guides, and have found surprisingly that the load F is concentrated on an upper side surface of the hole in the reinforcing plate, as shown in FIG. 9, and the lower side surface of the inserting hole receives no load at all.
Accordingly, the objects of the invention are to solve the above-mentioned prior art problems, and to provide a sliding contact guide having high assembly efficiency, improved yield of material, and reduced overall weight, both in a pivoting guide and in a fixed guide.